prominence

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prominence A cloud-like feature, visible especially in Hα light, located in the Sun's corona but cooler and denser than the corona. Prominences have temperatures of around 10 000 K, typical of the solar chromosphere, and densities 100 times higher than the corona. They are often seen around the Sun's limb at total solar eclipses. In Hα light they can be seen silhouetted against the Sun's disk, when they are termed filaments. They are categorized as quiescent prominences or active prominences, according to their behaviour. Active-region prominences have rapid motions and last for only a few days, whereas quiescent prominences last for at least a month (one solar rotation). Between the relatively cool prominence material and the hot corona is a transition region or sheath in which temperatures range from 15 000 to 60 000 K. Prominences closely follow the magnetic inversion line, and are thought to be supported by magnetic fields. They are most frequent during the rising part of the solar cycle.

prom·i·nence / ˈprämənəns/ • n. 1. the state of being important or famous: she came to prominence as an artist in the 1960s| [in sing.] the commission gave the case a prominence which it might otherwise have escaped. 2. the fact or condition of standing out from something by physically projecting or being particularly noticeable: radiographs showed enlargement of the right heart with prominence of the pulmonary outflow tract. ∎  a thing that projects from something, esp. a projecting feature of the landscape or a protuberance on a part of the body: the rocky prominence resembled a snow-capped mountain. ∎  Astron. a stream of incandescent gas projecting above the sun's chromosphere.

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